The present invention relates generally to lasers and more particularly to a laser in which the laser medium is a single crystal of chromium-doped magnesium orthosilicate forsterite (Cr:Mg.sub.2 SiO.sub.4).
The use of lasers in science and industry has received wide acceptance in an ever increasing variety of applications. Lasers have found use in such diverse areas as range finding apparatus, optical surgery, optical printers, optical readers and metal drilling. Briefly, lasers operate on the principle of light amplification through stimulated emission of radiation and can create extremely intense concentrations of light. The coherent light beam produced in a laser cavity is amplified in a laser material. Materials which have been used as laser media include gases, liquids, glasses and single crystalline solids.
When single crystalline solids are utilized in lasers, the crystals are generally in the form of elongated rods. The structure of the crystalline material must be very nearly perfect, since any optical inhomogeneities will cause distortion and scattering of the laser beam and thereby reduce the intensity and coherence of the radiation. Imperfections in the crystal which adversely affect lasing performance include elastic strain, crystal misorientations, chemical concentration inhomogeneities, dislocations, inclusions and bubbles.
In U.S. Pat. No. 3,997,853 to R. C. Morris et al. there is disclosed a laser in which the host comprises a single crystal of beryllium aluminate (BeAl.sub.2 O.sub.4) doped with trivalent chromium ions, the single crystal being crystallographically oriented substantially along the a-c plane, at least 30 degrees removed from the b-axis, and having a chromium doping concentration ranging from about 0.005 to 1.0 atom percent.
In U.S. Pat. No. 4,272,733 to J. C. Walling et al., there is disclosed a high power, broadly wavelength-tunable laser system which comprises as the laser medium particular single crystals of chromium-doped beryllium aluminate (BeAl.sub.2 O.sub.4 :Cr.sup.3+) having the chrysoberyl structure, means for exciting the laser medium and tuning means. The laser may be operated over a broad temperature range from cryogenic temperatures to elevated temperatures. Elevated temperatures are preferred, however, since they result in higher laser gain. Emission is in a spectral range from red to infrared, and the laser is useful in the fields of defense, communications, isotope separation, photochemistry, etc.
In U.S. Pat. No. 4,019,156 to W. D. Fountain there is disclosed a Q-switched/mode-locked Nd:YAG laser oscillator employing simultaneous active (electro-optic) and passive (saturable absorber) loss modulation within the optical cavity. This "dual modulation" oscillator can produce transform-limited pulses of duration ranging from about 30 psec to about 5 nsec with greatly improved stability compared to other mode locked systems. The pulses produced by this system lack intrapulse frequency or amplitude modulation, and hence are ideally suited for amplification to high energies and for other applications where well-defined pulses are required. Also, the pulses of this system have excellent interpulse characteristics, wherein the optical noise between the individual pulses of the pulse train has a power level well below the power of the peak pulse of the train
In U.S. Pat. No. 4,464,761 to R. R. Alfano, et al. a laser system in which the laser medium is a single crystal of Be.sub.3 A.sub.2 (SiO.sub.3).sub.6 :Cr.sup.3 (Emerald) is disclosed. Because of its wide fluorescence bandwidth, the material is suitable for high intensity, tunable, mode-locked pulses with durations as short as 10-500 femtoseconds. A number of different laser systems containing this laser medium are described.
In an article entitled Color by Kurt Nassau appearing in Scientific America, Oct. 1980. Volume 243, Number 4, pp. 124-156, various properties of Ruby, alexandrite and Emerald are discussed.